Self-repairing borehole wall stabilizer, preparation method thereof and drilling fluid

Abstract

The invention provides a self-repairing borehole wall stabilizer. The self-repairing borehole wall stabilizer is prepared from the following raw materials: 2.0 to 2.5 weight percent of cross-linking agent, 0.6 to 1.2 weight percent of early strength agent, 28 to 32 weight percent of organic silicon microcapsule, 15 to 18 weight percent of silicate microcapsule and 48 to 52 weight percent of chitosan. The invention also provides a preparation method of the self-repairing well wall stabilizer and a drilling fluid containing the self-repairing well wall stabilizer. According to the self-repairing well wall stabilizer provided by the invention, the organic silicon microcapsule and the silicate microcapsule are mixed with the cross-linking agent and the early strength agent and then encapsulated in the chitosan shell, so that multiple capsules are formed, the plugging capacity is higher, the temperature resistance can reach 180 DEG C, and the self-repairing well wall stabilizer can be directly added into drilling fluid for use.

Description

Technical Field

[0001] This invention belongs to the field of drilling fluid additive technology, specifically relating to a self-healing wellbore stabilizer, its preparation method and application, and in particular a slow-release high-viscosity self-healing wellbore stabilizer, its preparation method and application. Background Technology

[0002] With the ever-increasing demand for oil and gas, the complexity of wellbores drilled during oil and gas exploration and development is also increasing, particularly the probability of encountering complex shale and mudstone sections, leading to a higher likelihood of complex accidents. Statistics show that losses due to complex accidents in shale and mudstone sections account for over 70% of total losses during drilling. Therefore, ensuring wellbore stability during drilling in shale and mudstone sections is paramount for safe drilling, and most treatment agents developed are specifically designed for this formation. Conventional wellbore stabilizers primarily inhibit shale and mudstone hydration and dispersion, including amine inhibitors, quaternary ammonium clay stabilizers, and inorganic salt inhibitors. Subsequently, new types of wellbore stabilizers have been developed, most of which are synthetic multi-component copolymers. Recently, attention has turned to nanoparticles for sealing shale and mudstone pores. However, due to the numerous factors affecting the performance of nanoparticles, most research has been confined to laboratory settings, with little field application. Jiang Guancheng et al. (Bionic Drilling Fluid Theory and Technology, Petroleum Industry Press) proposed using a chemical biomimetic method to generate a shell-shaped coating layer on the well wall through chemical reaction, thereby improving the stability of the well wall. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of current water-based drilling fluid wellbore stabilizers, which have poor coating effects. It proposes a slow-release, high-viscosity self-healing wellbore stabilizer, its preparation method, and a drilling fluid. The raw materials of the self-healing wellbore stabilizer include organosilicon microcapsules and silicate microcapsules. Under high temperature and high pressure conditions downhole (temperature 150℃~250℃, pressure 40MPa~100MPa), the organosilicon and sodium silicate are released and react rapidly with crosslinking agents and early-strength agents to form a highly viscous inorganic polymer. This polymer is then applied to the wellbore to repair it and improve its stability.

[0004] Therefore, in a first aspect, the present invention provides a self-healing wellbore stabilizer, the raw materials of which include: 2.0wt% to 2.5wt% crosslinking agent, 0.6wt% to 1.2wt% early strength agent, 28wt% to 32wt% organosilicon microcapsules, 15wt% to 18wt% silicate microcapsules and 48wt% to 52wt% chitosan.

[0005] In the self-healing wellbore stabilizer of the present invention, organosilicon microcapsules and silicate microcapsules are mixed with crosslinking agents and early strength agents and then encapsulated in a chitosan shell to form multiple capsules, which have stronger sealing ability and can withstand temperatures up to 180°C. They can be added directly to drilling fluid for use.

[0006] In the self-healing wellbore stabilizer of this invention, the edges of the organosilicon microcapsules contain numerous silicon-oxygen bonds, which can combine with exposed silicon-oxygen bonds in the mudstone and shale components of the formation to form a strong adhesive force, thereby achieving a good coating effect. The silicate microcapsules also contain numerous silicon-oxygen bonds at their outer ends, which can also combine with silicon-oxygen bonds on the wellbore wall and be firmly adsorbed onto the wellbore wall. At the same time, since silicon-oxygen bonds exist in both the organosilicon polymer and the silicate, there is also a strong interaction between the organosilicon polymer and sodium silicate. Under the action of the crosslinking agent, a high-strength coating layer can be formed. Moreover, the addition of an early-strength agent can accelerate the solidification of the organic polymer.

[0007] As a specific embodiment of the present invention, the raw materials of the organosilicon microcapsules include: tetramethyldivinyldisiloxane, polydimethylsiloxane, polydiethylsiloxane, organic solvent, furfuryl thiol, photosensitizer and urea-formaldehyde resin.

[0008] In the organosilicon microcapsules of the present invention, tetramethyldivinyldisiloxane, polydimethylsiloxane, and polydiethylsiloxane contain many silicon-oxygen bonds, which can combine with the exposed silicon-oxygen bonds in the mudstone and shale components of the strata to form a strong adhesive force, thereby achieving a better coating effect.

[0009] In a specific embodiment of the present invention, the mass ratio of tetramethyldivinyldisiloxane, polydimethylsiloxane, and polydiethylsiloxane is 1–1.5:1:1–1.8. Under the above ratio conditions, these three organosilicones—tetramethyldivinyldisiloxane, polydimethylsiloxane, and polydiethylsiloxane—exhibit excellent miscibility.

[0010] As a specific embodiment of the present invention, the mass ratio of the polydimethylsiloxane to the organic solvent is 1:3 to 5.5.

[0011] In a specific embodiment of the present invention, the mass ratio of furfuryl thiol to polydimethylsiloxane is 1:3 to 6.

[0012] In a specific embodiment of the present invention, the ratio of the amount of photosensitizer added to the mass of polydimethylsiloxane is 1:1.5 to 3.

[0013] In a specific embodiment of the present invention, the mass ratio of the added amount of urea-formaldehyde resin to that of polydimethylsiloxane is 6.5 to 10:1.

[0014] As a specific embodiment of the present invention, the structural formula of the polydimethylsiloxane is shown in formula (I).

[0015] ((CH3)2SiO)n(I)

[0016] In equation (I), n is the degree of polymerization, 6≤n≤15, preferably 6≤n≤9.

[0017] As a specific embodiment of the present invention, the structural formula of the polydiethylsiloxane is shown in formula (II).

[0018] ((C2H5)2SiO)m(II)

[0019] In formula (II), m is the degree of polymerization, 3≤m≤12, preferably 5≤m≤8.

[0020] As a specific embodiment of the present invention, the photosensitizer is selected from at least one of benzoin, benzoin dimethyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, benzophenone, 2,4-dihydroxybenzophenone, and micriton.

[0021] As a specific embodiment of the present invention, the structural formula of the urea-formaldehyde resin is shown in formula (III).

[0022] (CH2N(CH3)CON(CH3)CH2)x, (III)

[0023] In equation (III), x is the degree of polymerization, 5000≤x≤10000, preferably 6000≤x≤7200.

[0024] As a specific embodiment of the present invention, the organic solvent is selected from at least one of tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, and ethylene glycol butyl ether (also known as butyl ethylene glycol).

[0025] As a specific embodiment of the present invention, the method for preparing the organosilicon microcapsules includes:

[0026] S1. Tetramethyldivinyldisiloxane, polydimethylsiloxane, and polydiethylsiloxane are added to an organic solvent to carry out the first prepolymerization reaction;

[0027] S2. Add furfuryl mercaptan and photosensitizer, and carry out photopolymerization reaction under ultraviolet light;

[0028] S3. Add urea-formaldehyde resin, carry out the first reaction at the first temperature, and then carry out the curing and granulation reaction at the second temperature;

[0029] S4. Remove the remaining organic solvent from the mixture obtained from the curing and granulation reaction to obtain the product.

[0030] As a specific embodiment of the present invention, the conditions for the first prepolymerization reaction include: a temperature of 60 to 80°C, a stirring speed of 800 to 1200 rpm, and a time of 30 to 50 minutes.

[0031] As a specific embodiment of the present invention, the conditions for the photopolymerization reaction include: under ultraviolet irradiation, the temperature is 60-80°C, the stirring speed is 100-300 rpm, the time is 30-50 min, preferably the wavelength of the ultraviolet light is 300 nm-500 nm, and the power is 3000 W-000 W.

[0032] As a specific embodiment of the present invention, the conditions for the first reaction include: a first temperature of 160℃~200℃, a stirring speed of 4800rpm~5200rpm, and a time of 30min~50min.

[0033] As a specific embodiment of the present invention, the conditions for the curing granulation reaction include: a second temperature of 60℃~80℃, a stirring speed of 80rpm~120rpm, and a time of 30min~50min.

[0034] As a specific embodiment of the present invention, the raw materials of the silicate microcapsules include: silicate, inorganic alkali, alginate, a first solvent, a second solvent, and a curing agent. The silicate microcapsules of the present invention also contain many silicon-oxygen bonds at their outer ends, which can combine with silicon-oxygen bonds on the well wall, thus firmly adsorbing onto the well wall.

[0035] In a specific embodiment of the present invention, the mass ratio of the silicate to the inorganic base is 8 to 12.5:1.

[0036] In a specific embodiment of the present invention, the mass ratio of the inorganic base to the first solvent is 1:6.5 to 10.

[0037] In a specific embodiment of the present invention, the mass ratio of the added alginate to the inorganic alkali is 12 to 18.5:1.

[0038] In a specific embodiment of the present invention, the ratio of the amount of the second solvent added to the mass of the inorganic base is 6.5 to 10:1.

[0039] In a specific embodiment of the present invention, the ratio of the amount of curing agent added to the mass of inorganic alkali is 1 to 1.8:1.

[0040] In a specific embodiment of the present invention, the silicate is one of sodium silicate, potassium silicate, and sodium potassium silicate, preferably sodium silicate.

[0041] As a specific embodiment of the present invention, the structural formula of the sodium silicate is shown in formula (IV).

[0042] Na₂O·ySiO₂, (IV)

[0043] In equation (IV), y is the modulus (degree of aggregation), and 1.5 ≤ y ≤ 3.0.

[0044] In a specific embodiment of the present invention, the inorganic base is either NaOH or KOH, preferably NaOH.

[0045] As a specific embodiment of the present invention, the alginate is one of sodium alginate and potassium alginate, preferably sodium alginate, which is a brown algae such as kelp, or a by-product of iodine and mannitol extraction from Sargassum. More preferably, the sodium alginate is a natural polysaccharide mainly composed of β-D-mannuronic acid and α-L-guluronic acid.

[0046] As a specific embodiment of the present invention, the curing agent is selected from at least one of calcium chloride, calcium bromide and calcium nitrate.

[0047] As a specific embodiment of the present invention, the first solvent and the second solvent may be the same or different, and each is independently selected from water and ethanol.

[0048] As a specific embodiment of the present invention, the method for preparing the silicate microcapsules includes:

[0049] S10. Add silicate and inorganic base to the first solvent to carry out the second prepolymerization reaction;

[0050] S20, add alginate and a second solvent to carry out the second reaction;

[0051] S30. Add curing agent to carry out curing reaction;

[0052] S40. After the curing reaction is complete, remove the microcapsule product, wash it, and remove the remaining solvent.

[0053] As a specific embodiment of the present invention, the conditions for the second prepolymerization reaction include: a temperature of 80 to 100°C, a stirring speed of 2800 rpm to 3200 rpm, and a time of 30 min to 50 min.

[0054] As a specific embodiment of the present invention, the conditions for the second reaction include: a temperature of 80 to 100°C, a stirring speed of 2800 rpm to 3200 rpm, and a time of 20 min to 30 min.

[0055] As a specific embodiment of the present invention, the conditions for the curing reaction include: a temperature of 30 to 50°C, a stirring speed of 100 to 300 rpm, and a time of 30 to 50 minutes.

[0056] As a specific embodiment of the present invention, the crosslinking agent is selected from at least one of 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-isopropylimidazole.

[0057] As a specific embodiment of the present invention, the early strength agent is selected from at least one of sodium nitrite, triethanolamine and urea.

[0058] As a specific embodiment of the present invention, the chitosan is deacetylated chitin, the main component of which is polyglucosamine (1-4)-2-amino-BD glucose, with an N-deacetylation degree exceeding 95%.

[0059] As a specific embodiment of the present invention, the wellbore stabilizer is used in drilling fluid.

[0060] Therefore, in a second aspect, the present invention provides a method for preparing the above-mentioned self-healing wellbore stabilizer, comprising the following steps:

[0061] S100, add crosslinking agent and early strength agent to carry out the third reaction;

[0062] S200, add organosilicon microcapsules and silicate microcapsules to carry out the fourth reaction;

[0063] S300, add chitosan and proceed with the fifth reaction;

[0064] S400. After the reaction is complete, filter, collect the product, wash and remove the remaining solvent.

[0065] In a specific embodiment of the present invention, the mass ratio of the crosslinking agent to the early strength agent is 2 to 3:1.

[0066] As a specific embodiment of the present invention, the conditions for the third reaction include: a temperature of 80 to 100°C, a stirring speed of 2800 rpm to 3200 rpm, and a time of 30 min to 50 min.

[0067] As a specific embodiment of the present invention, the mass ratio of the organosilicon microcapsules to the early strength agent is 25-40:1.

[0068] As a specific embodiment of the present invention, the mass ratio of the silicate microcapsules to the early strength agent is 15-20:1.

[0069] As a specific embodiment of the present invention, the conditions for the fourth reaction include: a temperature of 80 to 100°C, a stirring speed of 2800 rpm to 3200 rpm, and a time of 30 min to 50 min.

[0070] In a specific embodiment of the present invention, the mass ratio of chitosan to early strength agent is 40-65:1.

[0071] As a specific embodiment of the present invention, the conditions for the fifth reaction include: a temperature of 80 to 100°C, a stirring speed of 100 to 500 rpm, and a time of 20 to 30 minutes.

[0072] Therefore, in a third aspect, the present invention provides a drilling fluid comprising the self-healing wellbore stabilizer described above or the self-healing wellbore stabilizer prepared by the above preparation method.

[0073] As a specific embodiment of the present invention, the amount of the self-healing wellbore stabilizer added is 2.0% to 5.0% of the drilling fluid mass.

[0074] As a specific embodiment of the present invention, the field application method of the self-healing wellbore stabilizer includes:

[0075] 1) Add 2.0–5.0 wt% self-healing wellbore stabilizer directly to the drilling fluid, and allow it to circulate with the drilling fluid;

[0076] 2) When entering a complex section, stop drilling and circulate for 3-6 hours. Due to the increase in temperature and pressure, chitosan is squeezed, deformed and broken, releasing organosilicon microcapsules and silicate microcapsules. Under the conditions of high temperature, high pressure and well wall fracture compression, these two microspheres also begin to release organosilicon and sodium silicate. Under the action of crosslinking agent and early strength agent, these two polymers react rapidly to generate a polymer with extremely high viscosity, which is quickly adsorbed on the well wall and produces a self-repairing effect on the well wall.

[0077] 3) After the repair is completed, the pressure difference between the drill string and the formation decreases, and the remaining unreacted chitosan microspheres continue to circulate in the drilling fluid;

[0078] 4) Normal drilling operations can be resumed.

[0079] Compared with the prior art, the present invention has the following beneficial effects:

[0080] In the self-healing wellbore stabilizer of the present invention, organosilicon microcapsules and silicate microcapsules are mixed with crosslinking agents and early strength agents and then encapsulated in a chitosan shell to form multiple capsules, which have stronger sealing ability and can withstand temperatures up to 180°C. They can be added directly to drilling fluid for use.

[0081] In the self-healing wellbore stabilizer of this invention, the edges of the organosilicon microcapsules contain numerous silicon-oxygen bonds, which can combine with exposed silicon-oxygen bonds in the mudstone and shale components of the formation to form a strong adhesive force, thereby achieving a good coating effect. The silicate microcapsules also contain numerous silicon-oxygen bonds at their outer ends, which can also combine with silicon-oxygen bonds on the wellbore wall and be firmly adsorbed onto the wellbore wall. At the same time, since silicon-oxygen bonds exist in both the organosilicon polymer and the silicate, there is also a strong interaction between the organosilicon polymer and sodium silicate. Under the action of the crosslinking agent, a high-strength coating layer can be formed. Moreover, the addition of an early-strength agent can accelerate the solidification of the organic polymer. Detailed Implementation

[0082] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0083] The self-healing wellbore stabilizer provided by this invention comprises the following raw materials: 2.0wt% to 2.5wt% crosslinking agent, 0.6wt% to 1.2wt% early strength agent, 28wt% to 32wt% organosilicon microcapsules, 15wt% to 18wt% silicate microcapsules, and 48wt% to 52wt% chitosan.

[0084] The preparation methods of organosilicon microcapsules include:

[0085] 1) Add 360-420g of tetramethyldivinyldisiloxane, 280-360g of polydimethylsiloxane, 420-480g of polydiethylsiloxane and 1200-1500g of tetrahydrofuran sequentially to a high-pressure reactor. Raise the system temperature to 60-80℃, stir at 800-1200rpm, and allow the prepolymerization reaction to proceed for 30-50min.

[0086] 2) Add 60-90g furfuryl mercaptan and 120-150g photosensitizer to the above reactor in sequence, reduce the stirring speed to 100-300rpm, and expose the reaction to ultraviolet light (wavelength 420nm, power 4000W) for 30-50min of photopolymerization.

[0087] 3) Add 2500-2800g of urea-formaldehyde resin to the above reactor, raise the system temperature to 180℃, increase the stirring speed to 5000rpm, continue the reaction for 30-50min, then lower the temperature to 60-80℃, reduce the stirring speed to 100rpm, and allow the curing and granulation reaction to proceed for 30-50min.

[0088] 4) After the reaction is complete, the system is transferred to a rotary evaporator to remove the remaining solvent. The resulting microcapsules are organosilicon microcapsules.

[0089] The preparation methods for silicate microcapsules include:

[0090] 1) Add 1200-1500g silicate, 120-150g inorganic alkali and 1000-1200g deionized water to a high-pressure reactor in sequence, raise the system temperature to 80-100℃, stir at 2000-4000rpm, and perform prepolymerization reaction for 30-50min.

[0091] 2) Add 1800-2200g of sodium alginate and 1000-1200g of deionized water to the reactor in sequence, and continue the reaction for 20-30 minutes;

[0092] 3) Add 160-200g of curing agent to the above reactor, reduce the system temperature to 30-50℃, reduce the stirring speed to 100-300rpm, and cure for 30-50min;

[0093] 4) After the reaction is complete, the microcapsules are taken out and washed three times with deionized water. They are then transferred to a rotary evaporator to remove the remaining solvent. The resulting microcapsules are silicate microcapsules.

[0094] Example 1

[0095] 1) Preparation of organosilicon microcapsules:

[0096] (1) 360g of tetramethyldivinyldisiloxane, 280g of polydimethylsiloxane ((CH3)2SiO)6, 420g of polydiethylsiloxane (((C2H5)2SiO)5) and 1200g of tetrahydrofuran were added sequentially to a high-pressure reactor. The temperature of the reaction system was raised to 60℃ and the stirring speed was 1000rpm. The prepolymerization reaction was carried out for 30min.

[0097] (2) Add 60g furfuryl mercaptan and 120g benzoin to the reactor in sequence, reduce the stirring speed to 200rpm, and expose the reaction system to ultraviolet light (wavelength 420nm, power 4000W) for photopolymerization reaction for 30min.

[0098] (3) Add 2500g of urea-formaldehyde resin ((CH2N(CH3)CON(CH3)CH2) to the above reactor. 6000 The temperature of the reaction system was increased to 180℃, the stirring speed was increased to 5000rpm, and the reaction was continued for 30min. Then the temperature was reduced to 60℃, the stirring speed was reduced to 100rpm, and the solidification and granulation reaction was carried out for 30min.

[0099] (4) After the reaction is complete, the reaction system is transferred to a rotary evaporator to remove the remaining solvent. The resulting microcapsules are organosilicon microcapsules.

[0100] (ii) Preparation of sodium silicate microcapsules:

[0101] (1) Add 1200g sodium silicate (modulus y in formula (IV) is 1.5), 120g NaOH and 1000g deionized water to a high-pressure reactor in sequence, raise the temperature of the reaction system to 80℃, stir at 3000rpm, and carry out a prepolymerization reaction for 30min.

[0102] (2) Add 1800g sodium alginate and 1000g deionized water to the reactor in sequence and continue the reaction for 20min;

[0103] (3) Add 160g of calcium chloride to the above reactor, reduce the temperature of the reaction system to 30℃, reduce the stirring speed to 200rpm, and carry out the curing reaction for 30min.

[0104] (4) After the reaction is complete, the microcapsules are taken out and washed three times with deionized water. They are then transferred to a rotary evaporator to remove the remaining solvent. The resulting microcapsules are sodium silicate microcapsules.

[0105] (III) Preparation of slow-release, high-viscosity, self-healing wellbore stabilizers:

[0106] (1) Add 80g of 2-ethyl-4-methylimidazolium and 30g of sodium nitrite to a high-pressure reactor in sequence, increase the temperature of the reaction system to 80℃, stir at 3000rpm, and react for 30min.

[0107] (2) Add 1200g of organosilicon microcapsules and 600g of sodium silicate microcapsules to the reactor in sequence, and continue the reaction for 30min.

[0108] (3) Add 2000g of chitosan to the above reactor, reduce the stirring speed to 300rpm, and continue the reaction for 20min;

[0109] (4) After the reaction is complete, vacuum filter the microspheres, wash them three times with deionized water, transfer them to a rotary evaporator to remove the remaining solvent, and obtain the slow-release high-viscosity self-healing well wall stabilizer.

[0110] Example 2

[0111] 1) Preparation of organosilicon microcapsules:

[0112] (1) 390g tetramethyldivinyldisiloxane, 320g polydimethylsiloxane ((CH3)2SiO)8, 450g polydiethylsiloxane (((C2H5)2SiO)6) and 1350g tetrahydrofuran were added sequentially to a high-pressure reactor. The temperature of the reaction system was raised to 70℃ and the stirring speed was 1000rpm. The prepolymerization reaction was carried out for 40min.

[0113] (2) 75g furfuryl mercaptan and 135g benzophenone were added to the reactor in sequence, the stirring speed was reduced to 200rpm, and the reaction system was exposed to ultraviolet light (wavelength 420nm, power 4000W) for photopolymerization reaction for 40min.

[0114] (3) Add 2650g of urea-formaldehyde resin ((CH2N(CH3)CON(CH3)CH2) to the above reactor. 6800 The reaction system temperature was raised to 180℃, the stirring speed was increased to 5000rpm, and the reaction was continued for 40min. Then the temperature was lowered to 70℃, the stirring speed was reduced to 100rpm, and the solidification and granulation reaction was carried out for 40min.

[0115] (4) After the reaction is complete, the system is transferred to a rotary evaporator to remove the remaining solvent. The resulting microcapsules are organosilicon microcapsules.

[0116] (ii) Preparation of sodium silicate microcapsules:

[0117] (1) Add 1350g sodium silicate (modulus y in formula (IV) is 2.2), 135g NaOH and 1100g deionized water to a high-pressure reactor in sequence, raise the temperature of the reaction system to 90℃, stir at 3000rpm, and carry out a prepolymerization reaction for 40min.

[0118] (2) Add 2000g sodium alginate and 1100g deionized water to the reactor in sequence and continue the reaction for 25min;

[0119] (3) Add 180g of calcium bromide to the above reactor, reduce the temperature of the reaction system to 40℃, reduce the stirring speed to 200rpm, and carry out the curing reaction for 40min.

[0120] (4) After the reaction is complete, the microcapsules are taken out and washed three times with deionized water. They are then transferred to a rotary evaporator to remove the remaining solvent. The resulting microcapsules are sodium silicate microcapsules.

[0121] (III) Preparation of slow-release, high-viscosity, self-healing wellbore stabilizers:

[0122] (1) Add 100g of 2-phenylimidazole and 45g of triethanolamine to a high-pressure reactor in sequence, increase the temperature of the reaction system to 90℃, stir at 3000rpm, and react for 40min.

[0123] (2) Add 1350g of organosilicon microcapsules and 750g of sodium silicate microcapsules to the reactor in sequence, and continue the reaction for 40min.

[0124] (3) Add 2250g of chitosan to the above reactor, reduce the stirring speed to 300rpm, and continue the reaction for 25min;

[0125] (4) After the reaction is complete, vacuum filter the microspheres, wash them three times with deionized water, transfer them to a rotary evaporator to remove the remaining solvent, and obtain the slow-release high-viscosity self-healing well wall stabilizer.

[0126] Example 3

[0127] 1) Preparation of organosilicon microcapsules:

[0128] (1) Add 420g tetramethyldivinyldisiloxane, 360g polydimethylsiloxane ((CH3)2SiO)9, 480g polydiethylsiloxane (((C2H5)2SiO)8) and 1500g tetrahydrofuran sequentially to a high-pressure reactor, raise the temperature of the reaction system to 80℃, stir at 1000rpm, and perform a prepolymerization reaction for 50min;

[0129] (2) Add 90g furfuryl mercaptan and 150g michidone to the reactor in sequence, reduce the stirring speed to 200rpm, and expose the reaction system to ultraviolet light (wavelength 420nm, power 4000W) for photopolymerization reaction for 50min.

[0130] (3) Add 2800g of urea-formaldehyde resin ((CH2N(CH3)CON(CH3)CH2) to the above reactor. 7200 The reaction system temperature was raised to 180℃, the stirring speed was increased to 5000rpm, and the reaction was continued for 50min. Then the temperature was lowered to 80℃, the stirring speed was reduced to 100rpm, and the solidification and granulation reaction was carried out for 50min.

[0131] (4) After the reaction is complete, the system is transferred to a rotary evaporator to remove the remaining solvent. The resulting microcapsules are organosilicon microcapsules.

[0132] (ii) Preparation of sodium silicate microcapsules:

[0133] (1) Add 1500g sodium silicate (modulus y in formula (IV) is 3.0), 150g NaOH and 1200g deionized water to a high-pressure reactor in sequence, raise the temperature of the reaction system to 100℃, stir at 3000rpm, and carry out a prepolymerization reaction for 50min.

[0134] (2) Add 2200g sodium alginate and 1200g deionized water to the reactor in sequence and continue the reaction for 30min;

[0135] (3) Add 200g of calcium nitrate to the above reactor, reduce the temperature of the reaction system to 50℃, reduce the stirring speed to 200rpm, and carry out the curing reaction for 50min.

[0136] (4) After the reaction is complete, the microcapsules are taken out and washed three times with deionized water. They are then transferred to a rotary evaporator to remove the remaining solvent. The resulting microcapsules are sodium silicate microcapsules.

[0137] (III) Preparation of slow-release, high-viscosity, self-healing wellbore stabilizers:

[0138] (1) Add 120g of 2-isopropylimidazolium and 60g of urea to a high-pressure reactor in sequence, increase the temperature of the reaction system to 100℃, stir at 3000rpm, and react for 50min.

[0139] (2) Add 1500g of organosilicon microcapsules and 900g of sodium silicate microcapsules to the reactor in sequence, and continue the reaction for 50min.

[0140] (3) Add 2500g of chitosan to the above reactor, reduce the stirring speed to 300rpm, and continue the reaction for 30min;

[0141] (4) After the reaction is complete, vacuum filter the microspheres, wash them three times with deionized water, transfer them to a rotary evaporator to remove the remaining solvent, and obtain the slow-release high-viscosity self-healing well wall stabilizer.

[0142] Comparative Example 1

[0143] The preparation method is the same as in Example 3, except that the amount of polydimethylsiloxane ((CH3)2SiO)9 added in the preparation of organosilicon microcapsules is 800g.

[0144] Comparative Example 2

[0145] The preparation method is the same as in Example 3, except that in the preparation of the slow-release high-viscosity self-healing well wall stabilizer, 1500g of organosilicon microcapsules are replaced with 1500g of sodium silicate microcapsules.

[0146] Comparative Example 3

[0147] The preparation method is the same as in Example 3, except that in the preparation of the slow-release high-viscosity self-healing well wall stabilizer, 900g of sodium silicate microcapsules are replaced with 900g of organosilicon microcapsules.

[0148] Comparative Example 4

[0149] The preparation method is the same as in Example 3, except that in the preparation of sodium silicate microcapsules, the amount of sodium silicate and inorganic base added is 2000g and 500g, respectively.

[0150] Application Example 1

[0151] Performance testing: Measured using a shale membrane testing instrument (SMT).

[0152] Preparation of bentonite-based slurry (4.0 wt% bentonite + 0.5 wt% Na2CO3): Add 400 mL of tap water to a high-strength stirring cup, and add 16 g of bentonite and 2 g of Na2CO3 while stirring continuously. Stir for 20 minutes, pausing at least twice during this period to scrape off the bentonite adhering to the container wall. Let it age at room temperature for 24 hours in a sealed container before use.

[0153] 2.0 parts by weight of self-healing wellbore stabilizer (prepared from Examples 1-3 and Comparative Examples 1-4, respectively) were added to 100 parts by weight of bentonite-based slurry to obtain corresponding test plugging agent samples. Each test plugging agent sample was coated onto the front and rear shale rocks respectively, and the shale plugging rate was tested. The plugging rate under normal temperature and 220℃ / 6MPa conditions was investigated. The results are shown in Table 1.

[0154] Table 1. Test results of sealing rate of different self-healing wellbore stabilizers in shale.

[0155]

[0156] As shown in Table 1, the self-healing wellbore stabilizer prepared in the examples significantly improved the plugging rate of the test plugging agent samples compared to the blank examples after its addition. The plugging capacity also slightly increased with the increase of silicon content in the organosilicon capsules and silicate capsules. All examples achieved a plugging rate exceeding 90%, and their plugging capacity remained stable even under conditions of 220℃ and 6MPa. In contrast, the plugging rates of Comparative Examples 1-4 were lower, with the highest plugging rate at room temperature below 80% and the highest at high temperature below 70%.

[0157] Subsequently, the strength of the coated membrane was measured. 2.0 parts by mass of self-healing wellbore stabilizer (prepared from Examples 1-3 and Comparative Examples 1-4, respectively) was added to 100 parts by mass of deionized water to obtain corresponding test membrane strength samples. Each test membrane strength sample was ultrasonically dispersed at 10,000 rpm for 3 hours. The resulting suspension was then poured into a tetrafluoroethylene template, spread out, and allowed to air dry naturally for 3 days to form a film. Finally, the formed film was dried at 60°C for 24 hours. Its tensile stress and flexibility were measured using a DSS-500 tensile testing machine. The results are shown in Table 2.

[0158] Table 2. Test results of film strength of different self-healing wellbore stabilizers

[0159]

[0160]

[0161] As shown in Table 2, the films formed by the self-healing wellbore stabilizers prepared in Examples 1-3 have a certain strength, with tensile stress all above 6.0 kg / mm². 2 The above-mentioned materials exhibit excellent flexibility and elasticity, resulting in strong wellbore stability and repair capabilities. While comparative examples 1-4 maintained good flexibility, their tensile stress was significantly reduced, all falling below 5.1 kg / mm². 2 This fully demonstrates the tensile strength of the self-healing wellbore stabilizer.

[0162] In summary, the self-healing wellbore stabilizer provided by this invention has stronger plugging ability, can withstand temperatures up to 180℃, and can be directly added to drilling fluid for use.

[0163] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A self-healing wellbore stabilizer, characterized in that, Raw materials include: Crosslinking agent 2.0wt%–2.5wt%, early strength agent 0.6wt%–1.2wt%, organosilicon microcapsules 28wt%–32wt%, silicate microcapsules 15wt%–18wt%, and chitosan 48wt%–52wt%.

2. The wellbore stabilizer according to claim 1, characterized in that, The raw materials for the organosilicon microcapsules include: tetramethyldivinyldisiloxane, polydimethylsiloxane, polydiethylsiloxane, organic solvent, furfuryl mercaptan, photosensitizer, and urea-formaldehyde resin; Preferably, the mass ratio of tetramethyldivinyldisiloxane, polydimethylsiloxane, and polydiethylsiloxane is 1–1.5:1:1–1.

8. Preferably, the mass ratio of the polydimethylsiloxane to the organic solvent is 1:3 to 5.5; Preferably, the mass ratio of furfuryl thiol to polydimethylsiloxane is 1:3 to 6; Preferably, the ratio of the amount of photosensitizer added to the mass of polydimethylsiloxane is 1:1.5 to 3; Preferably, the mass ratio of the urea-formaldehyde resin to the polydimethylsiloxane is 6.5 to 10:

1.

3. The stabilizer according to claim 2, characterized in that, The structural formula of the polydimethylsiloxane is shown in formula (I). ((CH3)2SiO)n(I) In formula (I), 6 ≤ n ≤ 15, preferably 6 ≤ n ≤ 9; and / or The structural formula of the polydiethylsiloxane is shown in formula (II). ((C2H5)2SiO)m(II) In formula (II), 3 ≤ m ≤ 12, preferably 5 ≤ m ≤ 8; and / or The photosensitizer is selected from at least one of benzoin, benzoin dimethyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, benzophenone, 2,4-dihydroxybenzophenone, and micritone; and / or The structural formula of the urea-formaldehyde resin is shown in formula (III). (CH2N(CH3)CON(CH3)CH2)x, (III) In formula (III), 5000≤x≤10000, preferably 6000≤x≤7200; and / or The organic solvent is selected from at least one of tetrahydrofuran, N-methylpyrrolidone, dimethyl sulfoxide, and ethylene glycol butyl ether.

4. The wellbore stabilizer according to claim 2 or 3, characterized in that, The method for preparing the organosilicon microcapsules includes: S1. Tetramethyldivinyldisiloxane, polydimethylsiloxane, and polydiethylsiloxane are added to an organic solvent to carry out the first prepolymerization reaction; S2. Add furfuryl mercaptan and photosensitizer, and carry out photopolymerization reaction under ultraviolet light; S3. Add urea-formaldehyde resin, carry out the first reaction at the first temperature, and then carry out the curing and granulation reaction at the second temperature; S4. Remove the remaining organic solvent from the mixture obtained from the curing and granulation reaction to obtain the product; Preferably, the conditions for the first prepolymerization reaction include: a temperature of 60–80°C, a stirring speed of 800–1200 rpm, and a time of 30–50 min; Preferably, the conditions for the photopolymerization reaction include: under ultraviolet irradiation, a temperature of 60-80°C, a stirring speed of 100-300 rpm, a time of 30-50 min, preferably with an ultraviolet wavelength of 300-500 nm and a power of 3000-5000 W. Preferably, the conditions for the first reaction include: a first temperature of 160°C to 200°C, a stirring speed of 4800 rpm to 5200 rpm, and a time of 30 min to 50 min; Preferably, the conditions for the curing and granulation reaction include: a second temperature of 60℃~80℃, a stirring speed of 80rpm~120rpm, and a time of 30min~50min.

5. The wellbore stabilizer according to any one of claims 1-4, characterized in that, The raw materials for the silicate microcapsules include: silicate, inorganic alkali, alginate, a first solvent, a second solvent, and a curing agent. Preferably, the mass ratio of the silicate to the inorganic base is 8–12.5:1; Preferably, the mass ratio of the inorganic base to the first solvent is 1:6.5 to 10; Preferably, the mass ratio of the added alginate to the inorganic base is 12-18.5:1; Preferably, the ratio of the amount of the second solvent added to the mass of the inorganic base is 6.5 to 10:1; Preferably, the mass ratio of the curing agent to the inorganic alkali is 1 to 1.8:1; Preferably, the silicate is one of sodium silicate, potassium silicate, and sodium potassium silicate, more preferably sodium silicate, and its structural formula is shown in formula (IV). Na₂O·ySiO₂, (IV) In equation (IV), 1.5 ≤ y ≤ 3.0; Preferably, the inorganic base is either NaOH or KOH, more preferably NaOH; Preferably, the alginate is one of sodium alginate and potassium alginate, more preferably sodium alginate, and even more preferably kelp (a brown algae), or a byproduct of iodine and mannitol extraction from Sargassum. Preferably, the curing agent is selected from at least one of calcium chloride, calcium bromide, and calcium nitrate; Preferably, the first solvent and the second solvent are the same or different, and are each independently selected from water and ethanol.

6. The wellbore stabilizer according to claim 5, characterized in that, The method for preparing the silicate microcapsules includes: S10. Add silicate and inorganic base to the first solvent to carry out the second prepolymerization reaction; S20, add alginate and a second solvent to carry out the second reaction; S30. Add curing agent to carry out curing reaction; S40. After the curing reaction is complete, remove the microcapsule product, wash it, and remove the remaining solvent. Preferably, the conditions for the second prepolymerization reaction include: a temperature of 80–100°C, a stirring speed of 2800–3200 rpm, and a time of 30–50 min; Preferably, the conditions for the second reaction include: a temperature of 80–100°C, a stirring speed of 2800–3200 rpm, and a time of 20–30 min; Preferably, the curing reaction conditions include: a temperature of 30–50°C, a stirring speed of 100–300 rpm, and a time of 30–50 min.

7. The wellbore stabilizer according to any one of claims 1-6, characterized in that, The crosslinking agent is selected from at least one of 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, and 2-isopropylimidazolium; and / or The early-strength agent is selected from at least one of sodium nitrite, triethanolamine, and urea; and / or The chitosan is deacetylated chitin.

8. The wellbore stabilizer according to any one of claims 1-7, characterized in that, The wellbore stabilizer is used in drilling fluid.

9. The method for preparing the self-healing wellbore stabilizer according to any one of claims 1-8, characterized in that, Includes the following steps: S100, add crosslinking agent and early strength agent to carry out the third reaction; S200, add organosilicon microcapsules and silicate microcapsules to carry out the fourth reaction; S300, add chitosan and proceed with the fifth reaction; S400 After the reaction is complete, filter, collect the product, wash and remove the remaining solvent. Preferably, the mass ratio of the crosslinking agent to the early strength agent is 2 to 3:1; Preferably, the conditions for the third reaction include: a temperature of 80–100°C, a stirring speed of 2800–3200 rpm, and a time of 30–50 min; Preferably, the mass ratio of the organosilicon microcapsules to the early strength agent is 25-40:1; Preferably, the mass ratio of the silicate microcapsules to the early-strength agent is 15-20:1; Preferably, the conditions for the fourth reaction include: a temperature of 80–100°C, a stirring speed of 2800–3200 rpm, and a time of 30–50 min; Preferably, the mass ratio of chitosan to early-strength agent is 40-65:1; Preferably, the conditions for the fifth reaction include: a temperature of 80–100°C, a stirring speed of 100–500 rpm, and a time of 20–30 min.

10. A drilling fluid, characterized in that, The self-healing wellbore stabilizer includes the self-healing wellbore stabilizer according to any one of claims 1-8 or the self-healing wellbore stabilizer prepared by the preparation method according to claim 9. Preferably, the amount of the self-healing wellbore stabilizer added is 2.0% to 5.0% of the mass of the drilling fluid.

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